Dirt particles, in particular swarf, dust, casting sand or else liquid droplets, may impair the function of industrially produced products, such as for example injection nozzles for internal combustion engines. The cleanliness of workpieces in industrial production processes is therefore of great importance. In industrial production plants, the cleanliness or soiling of workpieces must therefore be systematically examined. Examining cleanliness or soiling is important in particular before intermediate and final assembly operations.
In order to ensure consistent cleanliness of workpieces, it is known to examine their degree of soiling in production processes by means of random samples. For determining the degree of soiling of a workpiece in industrial production, the workpiece is usually rinsed off with liquid by an employee using a spray gun in an analyzing bath. The dirt particles on the workpiece are thereby removed from the workpiece and enter the rinsing liquid. The liquid with the dirt particles is then collected. It is filtered with a filter membrane. Dirt particles from the workpiece are thereby retained in the filter membrane. The filter membrane is subsequently weighed, in order to deduce from the weight of the filter membrane the degree of soiling of the workpiece. Since it is very laborious to examine all of the workpieces in a production process, often only random samples are examined.
However, this manual determination of a degree of soiling of workpieces is not only time-consuming but also imprecise. When the workpiece is rinsed off with liquid, there is the risk of the workpiece being contaminated.